Wireless communication systems often require devices to select signals within predetermined frequency bands. When these devices are implemented as bandpass filters, users can select a desired range of frequencies, known as a passband, and discard signals from frequency ranges that are either higher or lower than the desired range. The selectivity of a filter is measured by its “Q factor.” Higher Q filters have a narrower passband, and in some instances are more effective at discarding frequencies outside the passband, as compared to a lower Q filter.
Cavity filters are devices frequently used to implement bandpass filters. A cavity filter has a resonant frequency that is determined, in part, by the geometry of a cavity.